Sliding clasp fastener

ABSTRACT

A sliding clasp fastener which is provided has a pair of sliders for opening and closing the fastener in the forward direction and in the reverse direction, respectively. The fastener has a series of discrete coupling elements each having means for facilitating engagement of adjacent elements with minimum frictional resistance when the fastener is opened or closed in the reverse direction, such means comprising a pocket having a front end wall sloping at the outside of the pocket and being reinforced by rib means inside the pocket.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a sliding clasp fastener, more particularly tosuch a fastener which can be opened and closed in either of tworeciprocal directions.

2. Prior Art

A variety of sliding clasp fasteners or zippers are known which areequipped with a pair of sliders, providing an option for the user tomanipulate either of the two sliders to open or close the fastener fromeither direction. Such fasteners have coupling elements formed by press,injection or die-casting into a symmetrical mating structure, theelement in a row on one stringer tape having a prong engageable with agroove in the corresponding element on the opposite tape. One problemposed by such form of coupling elements is that while the fastener issmoothly operative with the slider moving in one or the forwarddirection, the operation becomes sluggish or otherwise defective whenthe slider is moved in the other or the reverse direction account of theprong on one stringer getting jammed in the groove or severely strikingagainst the front end wall of the groove on the mating stringer.

A means for coping with this problem is disclosed in Japanese Laid-OpenPatent Publication 58-116946 wherein the coupling element is dented atan outer marginal edge of the groove so as to reduce interacting impactwith the mating prong. However, such an element structure lacked, due toreduced contact area, an element-to-element coupling strength sufficientto withstand lateral pull or stresses applied perpendicularly to theplane of the fastener. Another difficulty was that the front end walldefining the groove is susceptible to deformation by repeated impingingcontact with the corresponding prong, resulting in weakenedinterengagement of the fastener stringers.

SUMMARY OF THE INVENTION

With a view to overcoming the foregoing difficulties of the prior art,the present invention is a sliding clasp fastener which can be openedand closed from either direction by a pair of sliders and which carriescoupling elements mutually engageable or disengageable with leastfrictional resistance even when the slider is moved along the fastenerin the reverse direction.

Another important object of the invention is to provide a sliding claspfastener having a pair of stringers which can be coupled together withsufficient strength to withstand stresses applied in a directionparallel or perpendicular to the plane of the fastener.

According to the invention, a sliding clasp fastener has couplingelements each including at one of its ends mounting portions and at theopposite end a coupling head portion, said head portion having anengaging prong and a pocket complementary in shape with the contour ofsaid prong, said element having a front end wall contiguous with saidhead portion and defining said pocket, said front end wall having anouter marginal surface tilted downwardly to form a guide slope andincluding a rib projecting from the inner surface of said end wall.

The invention will be better understood from the following descriptiontaken in conjunction with the accompanying drawings which illustrates byway of example some preferred embodiments of the invention. Likereference numerals refer to like or corresponding parts throughout theseveral views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one of a series of discrete couplingelements embodying the invention;

FIG. 2 is a longitudinal cross-sectional view of a coupling head portionof the element of FIG. 1;

FIG. 3 is a perspective view of a modified form of a coupling elementaccording to the invention;

FIG. 4 is a perspective view of another modified form of couplingelement according to the invention;

FIG. 5 is a longitudinal cross-sectional view of a portion of FIG. 4;

FIG. 6 is a plan view of a sliding clasp fastener having the couplingelements embodying the invention and a pair of sliders;

FIG. 7 is a schematic cross-sectional view on enlarged scale of adjacentcoupling elements showing the same in coupling condition within theinterior of a reversely operated slider;

FIG. 8 is a transverse cross-sectional view of a sliding clasp fastenershown under the influence of stresses applied upwardly in a directionperpendicular to the plane of the fastener;

FIG. 9 is a cross-sectional view of a coupling head portion shown in thecondition of FIG. 8;

FIG. 10 is a cross-sectional view of a punch and die apparatus employedto form the coupling element of FIG. 1; and

FIG. 11 is a perspective view of the punch of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2 there is shown an individual coupling element 10, itbeing one of a series of discrete formations embodying the presentinvention. The coupling element 10 is generally rectangular in shape andhas at one of its ends opposed leg portions 11, 11' definingtherebetween a substantially oblong aperture 12 for receiving, as iswell known, a beaded edge of a stringer tape as shown in FIG. 8. At theopposite end of the coupling element 10 is formed a coupling headportion 13 which includes an engaging prong 14 and a receiving groove orpocket 15 complementary in shape with the contour of the prong 14 asbetter shown in FIG. 2. The pocket 15 is defined by a front end wall 16,a rear end wall 17, side walls 18, 18' and a bottom wall 19, the bottomwall 19 being contiguous with the engaging prong 14. The front end wall16 has an outer marginal surface tilted downwardly to form a guide slope20 substantially coextensive with the width of the wall 16 for purposesto be hereafter described. There is formed a rib 21 integral with andprojecting from the inner surface of the front end wall 16 and having athickness increasing progressively toward the bottom wall 19 of thepocket 15, the rib 21 serving to provide reinforcement of the element 10as hereafter described.

FIG. 3 shows a modified form of coupling element 10 which issubstantially the same in construction as that of FIG. 1 and 2 exceptthat there are provided two laterally spaced ribs 21.

The coupling elements 10 shown in FIGS. 1, 2 and 3 may be mostconveniently and suitably formed by a press or by die-casting. Thecoupling element 10 of FIG. 1 in particular may be made by an apparatusshown in FIG. 10 which comprises a stationary die 22 and a movable punch23. A starting material of continuous length (not shown) may be providedat predetermined intervals with the guide slopes 20 conveniently at thestage of punching out or cutting into individual element blocks. Thisblock 10' is placed on the die 22 and worked by the punch 23 as shown inFIG. 10 whereby the coupling head portion 13 is produced with the prong14 formed with the material that has moved from the pocket 15, and atthe same time with the rib 21 formed by a complementary recess 24 in thepunch 23. The presence of the recess 24 is important as it serves toretain the desired dimensions of the guide slope 20, and were it not forsuch a recess, the slope 20 would be reduced in size or otherwisedeformed as a result of the movement of the material from the pocket 15.

FIGS. 4 and 5 show another modification of coupling element 10 which maybe formed by injection or die-casting and which is substantially thesame as that of FIG. 1 except that there is a laterally elongated rib21A which is formed along the inner upper marginal edge of the front endwall 16.

In FIG. 6, there is shown a complete sliding clasp fastener F whichcomprises a pair of identical stringers F₁ and F₂ each carrying alongits longitudinal beaded edge a series of discrete coupling elements 10of the construction above described and a pair of sliders S₁ and S₂respectively positioned at the opposite ends of the fastener. The upperslider S₁ opens and closes the fastener F in the forward direction. Thelower slider S₂ is the one which opens and closes the fastener F in thereverse direction, in which instance the coupling elements 10 embodyingthe invention function as desired. The behavior of adjacent couplingelements 10 on the opposed stringers F₁ and F₂ within the interior ofthe slider S₂ moving to close the fastener F is illustrated in FIG. 7,in which the engaging prong 14 of the element 10 on one stringer F₁moves around and in sliding contact with the outer surface of the frontend wall 16 of the neighboring element 10 in the opposite matingstringer F2 and slips into the pocket 15 in the latter element. Thiscoupling operation of adjacent elements 10 is facilitated by theprovision of the guide slope 20 which permits movement of the prong 14therealong into the pocket 15 with minimum frictional resistance.

The provision of the rib 21 is another feature of the invention in thatit serves to reinforce the front end wall 16 of the element 10 which hasbeen somewhat weakened as a result of forming the guide slope 20 at theouter surface of the wall 16.

The rib 21 provides sufficient reinforcement to retain the elements 10stably in interengaged position against forces applied verticallyupwardly (FIG. 8) as shown in FIGS. 8 and 9, or against lateral pulltending to spread apart the fastener stringers.

Although various minor modifications may be suggested by those versed inthe art, it should be understood that we wish to embody within the scopeof the patent warranted hereon, all such embodiments as reasonably andproperly come within the scope of our contribution to the art.

What is claimed is:
 1. A sliding clasp fastener of the type having apair of sliders for opening and closing the fastener from either of twodirections comprising a pair of identical stringers and a series ofdiscrete coupling elements mounted one each of the respective stringers,said coupling elements each including, at one of its ends, leg portionsdefining therebetween an aperture, and at the opposite end a couplinghead portion, said head portion having an engaging prong and a pocketcomplementary in shape with the contour of said prong, said head portionincluding a front end wall having an outer marginal surface facing awayfrom said leg portions and extending contiguous to said engaging prong,and a substantially flat inner surface facing away from said outermarginal surface and defining a side of said pocket, said outer marginalsurface having a portion sloping downwardly away from said pocket toform a guide slope, said head portion further including at least onereinforcement rib disposed exclusively on said flat inner surface andextending from an upper edge of said flat inner surface toward thebottom of said pocket, said reinforcement rib having a substantiallyuniform width throughout the length thereof and a flat top surface.
 2. Asliding clasp fastener according to claim 1, said reinforcement ribterminating far short of the bottom of said pocket.
 3. A sliding claspfastener according to claim 1, including two said reinforcement ribsspaced laterally from one another and terminating in the bottom of saidpocket.